Meng Jianzhou, Gao Peng, Wang Xiao, Guan Yan, Liu Yishuang, Xiao Chunling
Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Front Microbiol. 2020 Jan 15;10:3017. doi: 10.3389/fmicb.2019.03017. eCollection 2019.
The emergence of drug-resistant (Mtb) has hampered treatments for tuberculosis, which consequently now require novel agents to overcome such drug resistance. The genetically stable D-alanine-D-alanine ligase A (DdlA) has been deemed as an excellent therapeutic target for tuberculosis. In the present study, a competitive inhibitor (IMB-0283) of DdlA was obtained via high-throughput screening. The minimum inhibitory concentrations (MIC) of IMB-0283 for the standard and clinical drug-resistant Mtb strains ranged from 0.25 to 4.00 μg/mL, whereas the conventional inhibitor of DdlA, D-cycloserine (DCS), only inhibited the growth of the standard Mtb strain at 16 μg/mL. The lethal effect of IMB-0283 on Mtb was found to act intracellularly in a DdlA-dependent manner. Specifically, IMB-0283 prevented the synthesis of neonatal cell walls but did not damage mature cell walls. Compared with those of DCS, IMB-0283 exhibited lower cytotoxicity and a higher selective index (SI). At the same dosages of treatment, IMB-0283 reduced bacterial load (log CFU/mL) in an acute animal model from 5.58 to 4.40, while DCS did not yield any such treatment efficacy. Taken together, the lower cytotoxicity and more efficacious activity of IMB-0283 suggest that it is a promising lead compound for antituberculosis drug development.
耐药结核分枝杆菌（Mtb）的出现阻碍了结核病的治疗，因此现在需要新型药物来克服这种耐药性。基因稳定的D-丙氨酸-D-丙氨酸连接酶A（DdlA）被认为是治疗结核病的极佳靶点。在本研究中，通过高通量筛选获得了DdlA的竞争性抑制剂（IMB-0283）。IMB-0283对标准和临床耐药Mtb菌株的最低抑菌浓度（MIC）范围为0.25至4.00μg/mL，而传统的DdlA抑制剂D-环丝氨酸（DCS）仅在16μg/mL时抑制标准Mtb菌株的生长。发现IMB-0283对Mtb的致死作用以DdlA依赖的方式在细胞内起作用。具体而言，IMB-0283阻止新生细胞壁的合成，但不破坏成熟细胞壁。与DCS相比，IMB-0283表现出更低的细胞毒性和更高的选择性指数（SI）。在相同的治疗剂量下，IMB-0283在急性动物模型中将细菌载量（log CFU/mL）从5.58降低到4.40，而DCS没有产生任何这种治疗效果。综上所述，IMB-0283较低的细胞毒性和更有效的活性表明它是抗结核药物开发中一种有前景的先导化合物。
